230 mile contact

[MichaelLAX]

Good starting tip: I purchased the FT-857d at HRO Burbank before they shut down that store.

Bill @ HRO Anaheim referred me to John, N6AX, who ironically I was also referred to back in May to potentially recap my Drake TR4Cw and AC-3 power supply.

John is a Kenwood guy.

He never replied to my May email, but I got his phone number and had a nice chat with him!

He is available to update the FT-857d if and when I need it and he is willing to consider the Drake once I send him a YouTube video that describes the process in detail.

So, thanks for the tip! 

[n4gix]

My FT-857D has the " Portable Zero Escort" battery pack and side rails.

 

[MichaelLAX]

"Portable Zero Escort" - what a great looking tip!

Now I wish I had a 2nd FT-857d to put back into my backpack with my collapsable 80 - 6 meter vertical and eliminate carrying the very heavy Duracell PowerPack 600 12v 28Ah pack!

The FT-857d's are selling used for too much money these days.

Maybe a Yaesu FT-891 with an Anytone AT-779UV and then I can do GMRS, too, in the back pack with this battery (and my LDG AT-PROII tuner), will do it better!

[oneeyeross]

Let's see.  Earth curves 8 inches per mile, that's 8*230=1840 inches / 12 to get feet =153 feet 8 inches in 230 miles.  They have a 200 foot tower, so that's line of sight, sort of.  I could see that happen without ducting...  Awesome contact, regardless of ducting or line of sight.  I am happy to get a signal through the trees from the other side of the reprod planting...

 

[JLeikhim]

My distance to horizon calculator begs to differ...

Sent from my SM-T350 using Tapatalk

[WRNA236]

8 hours ago, oneeyeross said:

Let's see.  Earth curves 8 inches per mile, that's 8*230=1840 inches / 12 to get feet =153 feet 8 inches in 230 miles.  They have a 200 foot tower, so that's line of sight, sort of.  I could see that happen without ducting...  Awesome contact, regardless of ducting or line of sight.  I am happy to get a signal through the trees from the other side of the reprod planting...

That 8" per mile rule of thumb tells you from your eye level how far the horizon is away from you if you're laying on the surface. 

If you're off the deck it's not a straight linear calculation because you're perpendicular to a curved surface and your view is a line tangent to the horizon to something else perpendicular to its surrounding chunk of the sphere..

 

The formula you use is:

So if your eyes are about 5 feet above the surface the horizon appears to be about 3 miles, not 7 like the 8 inches per mile would say.

Then if you have two observers trying to talk on perfectly flat ground that means the most they can be apart is 6 miles, each seeing 3 miles and meeting in the middle at their common tangent intersection.  Note that this is the optical line of sight, in reality you can see and radios can hear beyond the horizon due to diffraction, which in this case complicates the basic geometry.

 

Remember that "flat" is relative.  You're actually perpendicular to the surface of a round object. 

So the question is how tall does something have to be relative to the surface for you to see it.  This calculator introduces that using the concept of an "obscured part."

https://www.omnicalculator.com/physics/earth-curvature#how-far-can-i-see-before-the-earth-curves

So if your observation point is 5 feet high and the distance over the curved surface of the sphere is 230 miles the object has to be 34,414 feet tall for you to see the top of it.  If you move your observation point to 200 feet the horizon becomes 17.3 miles away but something 230 miles away from still needs to be 30,144 feet tall.

Think about it with things you know.  Like a city skyline.  When you're driving into any city with tall buildings you can watch something several hundred or thousands of feet tall come into view as you travel just fractions of a mile on the surface of the Earth.

Also the military relies on this heavily, particularly for radar and for pilots and ships.  Their height or altitude is a critical way to stay obscured or knowing how high something should be so you have a clue to how far away they are.  For a radar antenna 100 feet high you can only see 12 nautical miles away, for example.

https://www.rfcafe.com/references/electrical/ew-radar-handbook/radar-horizon-line-of-sight.htm

 

 

 

[AdmiralCochrane]

This is why sailing ships had an observer riding in a "crow's nest" high in the rigging. 

[mbrun]

That 8" per mile rule of thumb tells you from your eye level how far the horizon is away from you if you're laying on the surface. 
If you're off the deck it's not a straight linear calculation because you're perpendicular to a curved surface and your view is a line tangent to the horizon to something else perpendicular to its surrounding chunk of the sphere..

 
The formula you use is:

So if your eyes are about 5 feet above the surface the horizon appears to be about 3 miles, not 7 like the 8 inches per mile would say.
Then if you have two observers trying to talk on perfectly flat ground that means the most they can be apart is 6 miles, each seeing 3 miles and meeting in the middle at their common tangent intersection.  Note that this is the optical line of sight, in reality you can see and radios can hear beyond the horizon due to diffraction, which in this case complicates the basic geometry.

 
Remember that "flat" is relative.  You're actually perpendicular to the surface of a round object. 

So the question is how tall does something have to be relative to the surface for you to see it.  This calculator introduces that using the concept of an "obscured part."
https://www.omnicalculator.com/physics/earth-curvature#how-far-can-i-see-before-the-earth-curves

So if your observation point is 5 feet high and the distance over the curved surface of the sphere is 230 miles the object has to be 34,414 feet tall for you to see the top of it.  If you move your observation point to 200 feet the horizon becomes 17.3 miles away but something 230 miles away from still needs to be 30,144 feet tall.
Think about it with things you know.  Like a city skyline.  When you're driving into any city with tall buildings you can watch something several hundred or thousands of feet tall come into view as you travel just fractions of a mile on the surface of the Earth.
Also the military relies on this heavily, particularly for radar and for pilots and ships.  Their height or altitude is a critical way to stay obscured or knowing how high something should be so you have a clue to how far away they are.  For a radar antenna 100 feet high you can only see 12 nautical miles away, for example.
https://www.rfcafe.com/references/electrical/ew-radar-handbook/radar-horizon-line-of-sight.htm
 
 
 

Great explanation and graphics to make it understandable. The contents of your post belongs in a sticky of GMRS basics here on the forum.


Michael
WRHS965
KE8PLM

[OldRadioGuy]

Looks like the scadacore tool believes in a flat earth! 

Probably the paid version includes curvature but the free version leaves it out.

 

Vince

[oneeyeross]

See, that's why I stuck with chemistry and microbiology and didn't try to do geometry and all that kind of stuff!  Thanks for that explanation, I am going to copy it and read it a bunch until I get it right.

[WRNA236]

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